Method of making a concrete plug

ABSTRACT

A METHOD OF MAKING A CONCRETE PLUG COMPRISING THE STEPS OF PROVIDING AN ANHYDROUS CEMENT MIX, MOISTURIZING THIS MIX SLIGHTLY TO PARTIALLY HYDRATE THE MIX AND PROVIDE FOR PARTICLE GROWTH, PRESSING THE PARTIALLY HYDRATED MIX INTO A SLUG AND THEN GRINDING THE SLUG TO CREATE A MIX HAVING A PREDETERMINED PARTICLE SIZE LARGER THAN THAT OF THE STARTING MIX, PRESSING THE MIX INTO PLUGS OF FINAL FORM,   WETTING THE PLUGS TO START COMPLETE HYDRATION, AND COMPLETELY HYDRATING THE PLUG UNDER AMBIENT CONDITIONS.

Feb. 1, 1972 w. J. sTEFFAN 3,639,555

METHOD OF MAKING A CONCRETE PLUG Filed Nov. 21, 1969 44 CEMENT QUICK SETARLY STRENGTH FIG. 3.

CEMENT k PARTIAL HYDRATION EEEN fiE F DRY BLEND I I FOR PARTICLE GROWTHl l I I Y H DRATE QUALITY CONTROL SPECTRO'GRAPHIC I SLUG FORMINGCOLOR/NT OPERATION COLORANT I GO NO GRANULATE a so SCREEN QUALITYCONTROL I APPEARANCE Fla 2 I LUBRICANT 7 l I I I I A L IP HTIE A FINALHYDRATION CONFIGURATION INVENTOR. FINAL AIR CURE '|N$pECT|QN W/LL/AMJ.STEFFAN l Md/ M ATTORNEYS United States Patent 3,639,555 METHOD OFMAKING A CONCRETE PLUG William J. Stelfan, Fremont, Calif, assignor toBurke Concrete Accessories, Inc., Burlingame, Calif. Filed Nov. 21,1969, Ser. No. 878,786 Int. Cl. 1528b 3/00 US. Cl. 264140 9 ClaimsABSTRACT OF THE DISCLOSURE A method of making a concrete plug comprisingthe steps of providing an anhydrous cement mix, moisturizing this mixslightly to partially hydrate the mix and provide for particle growth,pressing the partially hydrated mix into a slug and then grinding theslug to create a mix having a predetermined particle size larger thanthat of the starting mix, pressing the mix into plugs of final form,wetting the plugs to start complete hydration, and completely hydratingthe plug under ambient conditions.

The present invention relates to the art of manufacturing concrete plugsand, more particularly, to the manufacture of concrete plugs to beemployed in the construction industry.

In the construction industry, concrete forms are often employed in theformation of concrete walls and the like. Frequently, such formscomprise panels held in opposed relationship by tie rods extendingtherebetween. Wet concrete is then poured between the panels and allowedto harden in the shape defined by said panels. When the concrete hashardened the panels are removed for subsequent reuse.

It is obvious that in the foregoing operation some means must beprovided to provide the proper spacing between the form panels. Thereare a number of approaches for accomplishing this. According to oneprior art arrangement, spacers are mounted on the rods for abuttingengagement with the inner surfaces of the panels and waler brackets areemployed to force the panels against the spacers. To avoid certaindisadvantages inherent with this arrangement other approaches have beendevised wherein the rod spacers are eliminated and wherein sealing andgrouting cores are disposed about the rods to prevent leakage of fluidconcrete around the rods and permit architectural finishing after thepanels are removed. 'Reference may be had to commonly assigned copendingUS. patent application Ser. No. 824,359, filed Apr. 30, 1969, for anarrangement wherein sealing and grouting cores are employed.

This application concerns itself with the manufacture of concrete plugsutilized for architectural finishing purposes after the panels areremoved. Plugs are commonly used after removal of the panels to fill indepressions created in the concrete upon removal of the tie rod spacers,sealing and grouting coresand the like along with the panels. It shouldbe understood, however, that the plugs manufactured in accordance withthe teachings of the present invention may be used generally to fill inany external void spaces found in a concrete structure.

Finishing plugs of the above described type have been commonlymanufactured in the prior art by molding the cement material of the plugin a wet condition. This prior art method of manufacture is quitedifficult and produces a plug which is of relatively low compressivestrength, thus resulting in a high frequency of plug breakage duringuse.

It is therefore an object of the present invention to provide a methodof manufacturing a concrete plug which results in the formation of aplug having a high degree of durability.

'ice

It is a further object of the present invention to provide a method ofmanufacutring a cnocrete plug which enables the manufacturer to maintaina high degree of control over the appearance and quality of the finishedplug.

These and other objects have been attained according to the teachings ofthe present invention by providing a method of manufacturing a concreteplug comprising the steps of providing an anhydrous cement mix,moisturizing this mix slightly (i.e. 2 to 3% moisture by weight) topartially hydrate the mix and provide for particle growth, pressing thepartially hydrated mix into a slug and then grinding the slug to createa mix having a predetermined particle size larger than that of thestarting mix, pressing the mix into plugs of final form, wetting theplugs to start complete hydration, and completely hydrating the plugunder ambient conditions.

The above noted and other objects of the present invention will becomemore apparent when viewed in light of the accompanying drawings,wherein:

FIG. 1 is a perspective view illustrating a concrete wall cross sectionhaving a depression in which a plug manufactured according to the methodof the present invention is positioned;

FIG. 2 is a diagrammatic flow-sheet presentation depicting the processesof the present invention;

FIG. 3 is a longitudinal cross sectional view illustrating a die cavityand punch arrangement employed during manufacture of a concrete plug inaccordance with the teachings of the present invention.

In FIG. 1 a typical construction situation is illustrated calling foruse of a concrete plug of the type manufactured according to theteachings of the present invention. More specifically, a portion of aconcrete wall 20 is shown which has at least one externalarchitecturally finished surface 22. It may be assumed that wall 20 hasbeen constructed utilizing a form molding process as described above. Aportion of the tie rod 24 which was used to hold the form panels (notshown) in position is illustrated. It should be noted that tie rod 24communicates with a recess 26 formed in the wall and having a coneshaped configuration. If it is desired to provide the wall with anesthetically pleasing appearance a plug 28 generally conforming to theshape of recess 26 is positioned in the wall in the manner illustratedso that the fiat outer surface of the plug is flush with finishedsurface 22 of the wall.

It is to be understood that the teachings of the present invention maybe employed in constructing a concrete plug of any configuration andthat it is not limited to formation of a cone-shaped plug. Theconfigurations of plug 28 and recess 26 and the placement and structureof tie rod 24 are shown for purposes of illustration only. Thearrangement shown is typical for that found when the apparatus andmethod disclosed in the aforementioned copending UJS. application Ser.No. 824,359 are utilized. In this instance recess 26 has been created byremoval of a cone-shaped grouting core employed in that invention,however, as previously stated, the recess 26 may be of any size andconfiguration such, for example, as that formed by removal of tie rodspacers utilized in an alternative prior art approach. The plug size andconfiguration will, of course, be chosen based on the dimensionalcharacteristics of the recess formed in the concrete structure. Inaddition, it is normally desirable to have the texture and color of theplug conform as nearly as possible to those of the structure with whichit is associated. A further desirable characteristic of a plug of thisnature is that it be capable of withstanding the stresses encounteredwhen positioning it in its associated recess, as when the plug ispressed thereinto. Generally, the plug is held in place with a suitableadhesive and to accommodate this adhesive the plug is proportioned to beslightly smaller than the recess so that it will seat with its externalsurface flush with that of the structure in which the recess is formed.

The method of manufacturing a plug according to the present inventionwill now be described in detail with particular reference to the flowdiagram of FIG. 2. The first step to be carried out in the manufactureof a plug is the preparation of an anhydrous cement mix or dry blend. Incarrying out the teachings of the present invention it has been foundparticularly advantageous to provide three principal dry blendcomponents. The three principal components are a cement chosen for itsquick set, early strength characteristics, a cement having longtermstrength development characteristics and hydrated lime. In addition,color may be added to the anhydrous cement mix where color of the plugto be manufactured is a factor.

One type of quick set cement suitable for use in carrying out theteachings of the present invention is Lumnite cement and a suitablecement having long-term strength characteristics is a type known aswhite cement. Lumnite cement is calcium aluminate and is sold under thename Lumnite by Universal Atlas Cement Co. of Pittsburgh, Pa. (adivision of US. Steel). These materials are well known in the concreteart. The elements of the dry blend are preferably mixed by weight toprovide a suitable anhydrous cement mix. Assuming that the cements givenas examples above are employed in the mix it has been found that asuitable dry blend is created when the Lumnite cement constitutes in theorder of 42.5% by weight of the mix, the white cement in the order of52.0% by weight of the mix and the hydrated lime in the order of byweight of the mix. Each of these components, however, may vary plus orminus of the base percentages given without harmful effect. Examples ofsuitable colorants which may be employed in the mix are yellow ironoxide and green iron oxide, although, as stated above, colorants need beadded to the mix only where color of the finished product is a necessaryfactor. When the mix percentages of the major components are those setforth above the desired colorants will add up to 0.5% by weight of thefinal dry blend.

In carrying out the blending operation any suitable commercial equipmentmay be utilized. For example, a horizontal ribbon mixer and entoleterarrangement may be utilized to mix the dry blend and to achieve uniformcolor. Suitable units of this nature are the 3,000 pound capacityhorizontal ribbon mixer manufactured by A.E. Paulsen Company, LosAngeles, Calif. and the Model 10 H.P. 3,000 pound capacity unitmanufactured by Entoleter Inc., New Haven, Conn.

The blended material preferably is subjected to a spectrographic qualitycontrol inspection before the next step in the manufacturing process iscarried out. Assuming the blend is properly mixed and the uniform coloris achieved, the anhydrous cement mix is partially hydrated by adding 2to 3% moisture by weight to the mix. This step provides for particlegrowth and otherwise prepares the mix for the next operation which willbe described below. In carrying out this partial hydration step onesuitable approach has been to spread the dry blend in a threeeighthsinch thick layer. The correct amount of water is then added by sprayingthe surface of the layer and the mix is allowed to set for hydration ofwetted particles. Another suitable approach would be to simply subjectthe mix to a controlled atmosphere of a relatively high humidity.

After the desired partial hydration of the mix has taken place thematerial is introduced into a suitable slugging machine such as theStokes Model R-4 so that it may be formed into slugs having sufficientstrength to withstand transit. The formed slugs are then introduced intoa grinder mechanism so that the material is reduced to granular form. Apiece of equipment suitable for this operation is the Stokes No. 43-CGranulator. This granulated form is desirable for carrying out the finalplug press operation which will be described in greater detail below. Agranular output density of 1.24 grams per cubic centimeter may beobtained when a one-eighth inch mesh screen is employed with the abovenoted piece of granulator equipment. A granular density of this orderhas been found to be quite suitable for proper performance of thefollowing operations.

The next principal step to be carried out in the manufacture of a plugis the press operation in which the plug is pressed into final form.However, before introduction of the granular material into the pressequipment it is desirable to add a suitable lubricant to facilitatepress die operation. Assuming the one-eighth inch granular size andoutput density of 1.24 grams per cubic centimeter suitable dielubrication may be provided by adding magnesium stearate to the grinderoutput within the range of 0.1% to 0.5% by weight.

After addition of the lubricant to the granular material the lubricatedgranular material is introduced into a suitable die press so that thedesired number of plugs may be formed to their final configuration. Onesuitable piece of equipment for carrying out this operation is theStokes Model 4 which, as stated above, may also be used in thepreliminary slugging operation. A suitable die arrangement for use inthis and similar pieces of equipment is shown in FIG. 3. Essentially,the die mechanisms comprises a die block 40, an upper punch 42 and alower punch 44. In operation, the cavity 46 defined by the die block isfirst filled with a predetermined quantity of the lubricated granularmaterial. Punches 42 and 44 are then moved toward one another by thepress equipment in a well-known manner to compress the graular materialcontained in the cavity. The formed plug is then ejected from themachine and conveyed to the next step in the operation. A compactionratio suitable for formation of a plug is 1.7:1 at 12.5 tons.

From the final press operation the formed plugs are introduced to waterto start the final hydration process. However, intermediate these twosteps the formed plugs are subjected to a quality control operationwhereby their apperance may be checked. Imperfect plugs are recirculatedback into the system through the granulation and screening equipmentwhile approved plugs are conveyed directly to the hydration site.Hydration is preferably carried out by introducing the formed plugs intoa suitable water absorption water tank for a time sufiicient to permitthe plugs to absorb water sufiicient to complete the hydration process.Complete hydration will normally be assured when the plugs have absorbedin the order of 11 to 14% of water by weight.

The final major step involved in the manufacture of the plugs is thestep of air curing. This may simply be accomplished by leaving the plugsexposed to ambient air for a predetermined period. After the curingprocess the plugs are subjected to a final inspection at which pointthey are packed and shipped to a job site or storedfor later use. Thefinal inspection stage may include a quality control check of theultimate compressive strength of the plugs. As stated above, throughutilization of the method according to the present invention, plugshaving a compressive strength in the order of 4,000 p.s.i. may beexpected to be produced. This contrasts with the relatively lowcompressive strength in the order of 600 p.s.i. of plugs produced usinga wet molding technique.

The exemplary embodiment of the method may be summarized as follows:

Step I.-Starting components (by weight):

Step II.--Mix starting components to blend together.

Step III.Partially hydrate mix by the addition of 2 to 3% moisture byweight to promote particle growth.

Step IV.Slug partially hyrated mix by compacting in a ratio of 1.7 to 1at 12.5 tons.

Step V.Grind slugged mix to A5 inch mesh screen size to produce agranular mix having a density of 1.24 grams/cm.

Step VI.Add 0.1 to 0.5% by weight of magnesium stearate to ground mixfor lubrication purposes.

Step VII.Press lubricated mix to final plug form by compacting in aratio of 1.7 to 1 at 12.5 tons.

Step VIII.Start final hydration by wetting formed plugs 11 to 14% byweight.

Step IX.Cure formed and wetted plugs in ambient air.

I claim as my invention:

1. A method of making a concrete plug comprising the steps of:

providing an anhydrous cement mix of particulated elements; partiallyhydrating the mix; forming the partially hydrated mix into a pluralityof particles having a size greater than the size of the anhydrous cementmix particulated elements by pressing the mix into slug form and thenreducing the pressed slugs to the desired particle size;

compressing the plurality of particles so that they assume the form of asolid plug; and,

hydrating the plug.

2. The method of claim 1 wherein the mix is partially hydrated by addingthereto 2 to 3% moisture by weight.

3. The method of claim 1 wherein the plug is hydrated by setting theplugs and curing the wetted plugs in the ambient atmosphere.

4. The method of claim 1 wherein a mold lubricant is added to theplurality of particles before compression thereof into solid plug form.

5. The mehod of claim 1 wherein the anhydrous cement mix is provided byblending together in dry form at least a quick-set cement, a cementhaving long term strength development characteristics, and hydratedlime.

6. The method of claim 1 including the additional step of screening theplurality of particles from the rest of the ground slugs prior tocompression of said particles into solid plug form.

7. The method of claim 5 wherein said quick-set cement is cement of thecalcium aluminate type and wherein said cement having long term strengthdevelopment characteristics is white cement.

8. The method of claim 5 wherein the anhydrous cement mix furtherincludes particulated colorant materials.

9. A method of making a concrete plug comprising the steps of providingan anhydrous cement mix of particulated elements comprising at least inthe order of 42.5 percent cement of the calcium aluminate type, 52.0percent white cement and 5 percent hydrated lime;

partially hydrating the mix by adding 2 to 3 percent moisture by weightto the mix; forming the partially hydrated mix into a plurality ofparticles having a density in the order of 1.24 grams per cubiccentimeter; adding magnesium stearate to the plurality of particleswithin the range of 0.1 percent to 0.5 percent by weight; compressingthe combined magnesium stearate and plurality of particles so that theyassume a solid .plug; and,

hydrating the plug by adding water within the range of 11 to 14 percentby weight thereto.

References Cited UNITED STATES PATENTS 732,674 6/1903 Bell et al.264'333 2,123,317 7/1938 Schless 264-333 2,572,510 10/1951 OrSini264-162 ROBERT F. WHITE, Primary Examiner G. AUVILLE, Assistant ExaminerUS. Cl. X.R.

264232, 294, 333, Dig 43

